1. Field of the Invention
The present invention relates to a wire saw which cuts a work by moving wires to which an abrasive liquid adheres while pressing the wires onto the work and to a cutting method thereof.
2. Description of the Related Art
A wire saw is used as a device for cutting various stick-shaped works such as magnetic materials, semiconductor materials, and ceramic materials. This wire saw is so structured that a wire repeatedly moving back and forth is wound between a pair of main rolls a plurality of times at regular spaced intervals, an abrasive liquid is supplied to the surface of the wires arranged at the regular spaced intervals to cause abrasive grains dispersing in the abrasive liquid to adhere to the wire, and the wires with the abrasive grains adhering thereto are moved while being pressed onto a work, thereby cutting the work into many plate-shaped pieces at one cutting operation.
In the conventional wire saw, a supply nozzle opening along the whole length of the work in a longitudinal direction thereof is disposed above the wire array immediately before entering the work and the abrasive liquid is dropped onto the wires from the supply nozzle, thereby supplying the abrasive grains to cut positions of the work. In this case, it is necessary that the abrasive grains adhere firmly enough onto the surfaces of a large number of the wires in order to obtain high efficiency in machining and high precision in cutting. Therefore, the abrasive liquid is prepared by mixing the abrasive grains in a liquid medium of oil or the like with a relatively high viscosity so that the abrasive grains easily adhere to the surfaces of the wires. Further, in order to uniformly supply the abrasive liquid over the entire length of the wires, used are a supply nozzle structured by a single tube whose diameter widens from an inlet port for the abrasive liquid toward its downstream side and a supply nozzle structured by combining two tubes with different diameters, thereby making it possible to supply the abrasive liquid uniformly over the whole length of the supply nozzle.
Chips adhering onto the surfaces of the wires after the work is cut are continuously washed away by the abrasive liquid. The chips washed away from the surfaces of the wires drop downward together with the abrasive liquid to be collected in a receiving vessel.
The conventional wire saw, however, has a problem that the supply nozzle is clogged in a short time due to fine grains and grinding dust (chips and sludge) which are caused by the cutting operation so that the amount of the abrasive grains adhering onto the wires is not uniform over the whole length of the work, thereby changing the thickness of the work and roughening the cut surfaces of the work. Further, since the clogging of the supply nozzle disenables the supply of the abrasive liquid onto the wires, thereby causing wire breakage, the problem is caused that the cutting work cannot be continued for a long time.
Further, in the conventional method in which the abrasive liquid is dropped right onto the wires from the supply nozzle, the abrasive grains adhere onto the wires only by surface tension of the abrasive liquid, and most of the abrasive grains drop off the wires, and therefore, the degree of their adhesiveness greatly varies depending on the viscosity of the abrasive liquid and the supply amount from the supply nozzle. Due to deterioration of flowability in accordance with the increase in the amount of the chips mixed therein, the abrasive liquid used for the cutting work for a long time stays at a horizontal pipe portion and the like when the operation of the wire saw is stopped, and the abrasive grains hang together in the pipe to easily clog the pipe. Moreover, the abrasive grains which hang together close the opening of the supply nozzle, which causes the wire breakage more often.
The present invention is made in view of the above and it is an object of the present invention to provide a wire saw which can cut a work in a good condition for a long time and to provide a cutting method thereof.
The present invention is a wire saw comprising a wire for cutting a work while being pressed onto the work and moving in an axial direction thereof, and an abrasive liquid, which is made by dispersing abrasive grains in a dispersion medium, interposed between the work and the wire, the wire saw being so structured that a flow of the abrasive liquid is formed and the wire moves under the liquid level of the abrasive liquid whose flow is formed.
For example, this wire saw is so structured that the abrasive liquid is continuously supplied to a vessel to cause the abrasive liquid to continuously flow out of an upper surface opening of the vessel and the wire moves under the liquid level of the abrasive liquid which is flowing out. In this case, the wire saw may also be so structure that a higher position and a lower position are provided on upper ends of side surfaces of the vessel and the abrasive liquid flows out at the lower position. Further, it is also suitable that a pair of main rolls for guiding the wire to move horizontally in the upper surface opening of the vessel are disposed on both sides of the vessel, the lower position is formed in a position lower than the wire which moves between these main rolls, and upper ends of circumferential surfaces of these main rolls are positioned higher than the lower position and lower than the higher position.
Another aspect of the present invention is a method of cutting a work in which, when the work is cut by moving a wire in an axial direction thereof while the wire is pressed onto the work and an abrasive liquid which is made by dispersing abrasive grains in a dispersion medium is interposed between the work and the wire, a flow of the abrasive liquid is formed and the wire is pressed onto the work while being moved under a liquid level of the abrasive liquid whose flow is formed.
According to the present invention, the work is cut in the abrasive liquid so that a sufficient amount of the abrasive grains can be supplied between the work and the wire for a long time. Thereby, the operation can be continued for a long time since wire breakage is prevented, and the surfaces of cut pieces of the work can be maintained in a uniform and good condition, which can greatly contribute to improvement in productivity of wire saw cutting.